Physiological adaptation to performance as crop plants

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Abstract
Morphological and cytogenetic changes associated with evolution from wild plant to cultivar have been explored for many crop plants, but the physiological adaptations are less well known. Selection for better performance as crops has not been associated with increase in relative growth rate or photosynthetic rate. In fact, photosynthetic rate per unit leaf area has fallen during the evolution of some crops, but this has been counterbalanced by greater leaf area and duration of photosynthetic activity. The capacity to transport assimilates to the storage organs has increased, due mainly to additional phloem differentiation rather than to closer proximity of source and sink organs. Greater size or number of storage organs, together with their more compact arrangement and more synchronous development, have all contributed to their predominance as a sink for assimilates and mobile nutrients towards the end of the life cycle, attracting progressively more substance to the organs harvested by man.
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